tailieunhanh - Cracking the Toefl IBT 2009 edition part 46

Welcome to the Princeton Reviews thorough test preparation guide for the Test of english as a Foreign Language. TOEFL In this book, you will find everything you need to prepare for the TOEFL—information on the test format, test-taking strategies, drills, and, of course, a full-length practice exam. | water. The mercury vapors helped fix the images to the plates and developed them. The chilled water kept the plates from breaking up during this critical step. The daguerreotypists next applied hydrosulfate soda to the plate surfaces to dissolve any bromo-iodine that had not been exposed to light and brushed them with a solution of gold and chlorine to brighten the images and sharpen their black-white contrast. There were difficulties for the daguerreotypists customers too. The expense of materials and labor was passed on to them in the form of very high prices. Only the rich could easily afford to sit for a daguerreotype portrait. For those of more limited means a daguerreotype was a once-in-a-lifetime treat. Additionally daguerreotype plates required long exposures from 8 to 20 minutes in order to yield high-quality images. Chairs and tables with special support were designed to help those posing for portraits to remain absolutely still throughout the exposure time. If they did not. the resulting image would be blurred. Not even the cleverest such design of course could compensate for the need of the human eye to blink periodically. For all the disadvantages involved in making daguerreotypes no one could argue with the finished product when things went well. The process recorded textural detail with a realism that still seems shocking. The sheen of satin and the dull heavy nap of flannel are easily distinguished. Those posing for daguerreotypes tired after trying to maintain the same facial expression for minutes at a time the result was that their features often relaxed into an attractive thoughtfulness. The incentive to develop a photographic process that retained the advantages of the daguerreotype without the disadvantages was thus powerful. The substitute with the most lasting popularity was the ferrotype or tintype which used an enamel-coated iron plate. 468 I Cracking the TOEFL iBT The Princeton Review TOEFL